IF THE WOMAN'S MOVEMENT had existed in Clementine Churchill's youth and caught her up in its values and life styles, what, one wonders, might have happened to Winston Churchill? Except for her shyness, there were the makings of a feminist. Clementine Hozier was a beauty, but at Berkhamsted High School she nursed dreams of going on to university, hopes that were sabotaged by a mother who was appalled at the thought her daughter might turn into a "blue-stocking." The young Mrs. Churchill considered her celebrated mother-in-law -- "Jennie" -- "vain and frivolous." She was "ardently in favour of votes for women" and "privately lobbied" her husband on its behalf -- with indifferent success. She was a better judge of character than he, tartly expressing her distaste for such Tory cronies as Beaverbrook, Birkenhead and Bracken. In her innermost feeling she was a radical, most content when her husband was with the Liberals. Had she been touched by the fires of feminism, she would have made a formidable public force.

But would she have been happier personally? Would Winston Churchill, had he been able to abide a feminist in his household, have served the English-speaking peoples as well as he did? The answers to these questions are by no means self-evident. It is one of the virtues of this beguiling book by Mary Soames, the youngest child of the Churchills, that she provides new and unique materials from the family archives so that readers can answer such questions for themselves. "One wonders what she is like underneath," Eleanor Roosevelt once asked. This exemplary book, written with honesty, affection and loyalty, would have helped dispel her puzzlement.

Clementine's grandmother, the aged Lady Airlie, when she heard of her granddaughter's engagement to Winston, wrote perceptively:

"Winston is his father over again, with the American driving force added. His mother and he are devoted to one another, and I think a good son makes a good husband. Clementine is wise. She will follow him and, I hope, say little."

Soames asserts that Lady Airlie underestimated her granddaughter's strength of character and independence, and the letters Clementine wrote during the 57 years of married life bear her out. They were peppered with astute comments on politics and politicians as well as with good advice to her husband. Thus, after the ill-starred Gallipoli campaign when Churchill seemed to be finished politically and sought restlessly for a way to make a comeback, she cautioned him, "Patience is the only grace you need," and he would have been better off had he heeded her advice. In the abdication crisis in the 1930s, she told him that he misread the mood of the country, that his advocacy of King Edward's cause would do him great harm, which it did. In 1942 after the fall of Singapore, when Churchill felt obliged to reconstruct his cabinet, she begged him to put his money on Laborite Sir Stafford Cripps, not on his Tory friend and current cabinet-member Lord Beaverbrook, who had recently given him "much difficulty."

She was politically aware and well informed and could have played a more active and prominent role in politics. But she chose, in part out of natural shyness, and in part out of recognition of the truth in Lady Airlie's advice, to follow her husband and say very little -- at least in public. "The real sphere of her influence and usefulness to him politically was in private," writes her daughter, "for the most part unseen, although not unrealized, by those who knew them well . . . . From the day she married him until his death fifty-seven years later, Winston dominated her whole life, and once this priority had been established, her children, personal pleasures, friends, and outside interests competed for what was left."

Such self-subordination exacted a price. Once she became "so enraged that she hurled a dish of spinach at Winston's head." On another occasion, exasperated by the men lingering on in the dining room after the women had gone to the drawing room, she showed her displeasure by marching the women off to bed. Knowing how much their country house Chartwell meant to her husband, she put up with the place, but she never liked it. Their conceptions of a "holiday" often clashed. He preferred the Riviera while she went to lodgings at Frinton by the sea. In her 50th year, still slim, elegant, beautiful, she went off, with Winston's reluctant consent, on a four-month, 30,000 mile cruise on Lord Moyne's yacht, a pleasure jaunt that included falling "romantically in love," with a fellow passenger, Terence Philip, whom Soames describes as "suave, goodlooking, charming, and cultivated."

But such escapes, explosions and clashes were all in the context of a deep, abiding and passionate love which to the very end of their lives both Clementine and Winston were able to declare to each other. Churchill knew the burdensome demands he placed upon her. "I am so devoured by egoism," he wrote her from France during World War I, "that I would like to have another soul in another world and meet you in another setting and pay you all the love and honour of the great romances."

And she knew the excitement and exhilaration of being married to the most extraordinary Englishman of the century. Soames herself nicely caught the rewards as well as the vexations of the marriage in a letter that she wrote her after the war when her mother's spirits were low:

"It seems to me such a triumph that after so many events -- which have all of them left their marks on your own private life and experience -- you and Papa should have come through still loving each other and still together.

"To me -- it is one of the most wonderful and admirable rocks to which I cling amid the daily evidence of ship-wrecked marriages -- & so many of them not even ship-wrecked -- but just deserted.

"For despite all his difficulties -- his overbearing -- exhausting temperament -- he does love you and needs you so much . . . .

"Your triumph is that you really have been and are -- everything to Papa. Many, many great men have had wives who ran their houses beautifully and lavished care and attention on them -- But they looked for love and amusement and repose elsewhere. And vice versa. You have supplied him with all these things -- without surrendering your own soul or mind."